Added St extension and modified Rx Gx to avoid conflict

Change-Id: Ie3a09088eae83e1dff82ff82051e6345c103c171
diff --git a/extensions/CMakeLists.txt b/extensions/CMakeLists.txt
index 96a8334..67963ef 100644
--- a/extensions/CMakeLists.txt
+++ b/extensions/CMakeLists.txt
@@ -118,6 +118,7 @@
 FD_EXTENSION_SUBDIR(dict_SLh "dict_SLh extension library" ON)
 FD_EXTENSION_SUBDIR(dict_Sd "dict_Sd extension library" ON)
 FD_EXTENSION_SUBDIR(dict_Sh "dict_Sh extension library" ON)
+FD_EXTENSION_SUBDIR(dict_St "dict_St extension library" ON)
 FD_EXTENSION_SUBDIR(dict_T4 "dict_T4 extension library" ON)
 FD_EXTENSION_SUBDIR(dict_T6aT6bT7 "dict_T6aT6bT7 extension library" ON)
 FD_EXTENSION_SUBDIR(dict_Tsp "dict_Tsp extension library" ON)